/*
* RgbAvg2Gray.java
*
* Created on August 27, 2006, 8:28 AM
*
* To change this template, choose Tools | Template Manager
* and open the template in the editor.
*
* Copyright 2007 by Jon A. Webb
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the Lesser GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package jjil.algorithm;
import jjil.core.Error;
import jjil.core.Gray8Image;
import jjil.core.Image;
import jjil.core.PipelineStage;
import jjil.core.RgbImage;
import jjil.core.RgbVal;
/**
* Pipeline stage converts an RgbImage into a Gray8Image. It does
* this by choosing at each pixel the value that will give the maximum
* contrast in the resulting image. That is, it computes
* the R, G, and B values at each pixel, and chooses the most extreme
* value -- the one largest in absolute value.
* @author webb
*/
public class RgbMaxContrast2Gray extends PipelineStage {
/** Implementation of push operation from PipelineStage.
* Pipeline stage converts an ARGB color image into a Gray8Image. It does
* this by choosing at each pixel the value that will give the maximum
* contrast in the resulting image. That is, it computes
* the R, G, and B values at each pixel, and chooses the most extreme
* value -- the one largest in absolute value.
* Note that the RGB→Gray conversion involves
* changing the data range of each pixel from 0→255 to -128→127
* because byte is a signed type.
*
* @param image the input image
* @throws jjil.core.Error if image is not an RgbImage
*/
public void push(Image image) throws jjil.core.Error {
if (!(image instanceof RgbImage)) {
throw new Error(
Error.PACKAGE.CORE,
ErrorCodes.IMAGE_NOT_RGBIMAGE,
image.toString(),
null,
null);
}
RgbImage rgb = (RgbImage) image;
int[] rgbData = rgb.getData();
Gray8Image gray = new Gray8Image(image.getWidth(), image.getHeight());
byte[] grayData = gray.getData();
for (int i=0; i<image.getWidth() * image.getHeight(); i++) {
/* get individual r, g, and b values, unmasking them from the
* ARGB word. The r, g, and b values are signed values
* from -128 to 127.
*/
byte r = RgbVal.getR(rgbData[i]);
byte g = RgbVal.getG(rgbData[i]);
byte b = RgbVal.getB(rgbData[i]);
int nAR = Math.abs(r);
int nAG = Math.abs(g);
int nAB = Math.abs(b);
if (nAR >= nAG && nAR >= nAB) {
grayData[i] = r;
} else if (nAG >= nAB) {
grayData[i] = g;
} else {
grayData[i] = b;
}
}
super.setOutput(gray);
}
}